In 2015, leaders from nearly every nation in the world met in Paris with hopes to mitigate the damaging consequences of global warming. Called the Paris Agreement, nations agreed that ambitious efforts should be made to keep the planet's warming limited to a 1.5-degree-Celsius rise by the century's end. Doing so would stave off the calamitous impacts of historic rainfall events, mega-droughts, and the melting of colossal ice sheets. The U.S. is the only country opposed to the agreement, with President Trump announcing he'd withdraw from the accord last year (he technically can't make it official until 2020).

But with this latest report, the IPCC found that in order to tame temperatures at around 1.5 degrees Celsius, carbon emissions must be profoundly reduced over the next decade, to just 45 percent of levels in 2010. Such a transition would be wholly unprecedented.

Technology isn't the only limiting factor. It's largely political. We know how to create energy without burning fossil fuels, but both heavily-industrialized and rapidly-industrializing nations would have to begin dramatically altering their energy production in just the next few years.

“Limiting warming to 1.5 C is possible within the laws of chemistry and physics but doing so would require unprecedented changes,” said Jim Skea, a leading IPCC scientist, in a statement.

Overall, the goal is even more ambitious: The IPCC concludes net carbon emissions need to fall to absolute zero by 2050.

But, even if these ambitious goals aren't met, researchers — like NASA climate scientist Gavin Schmidt — have underscored that the battle is not nearly lost. Making any sort of significant carbon emission reductions will still help our future cause, perhaps mightily.

I agree with @ABTagenda that framing this report as "we only have 10 years to act" as done by the @washingtonpost in their headline is neither correct nor helpful. Making better decisions on emissions is always going to be helpful - whether it's now, in 5 years or in 20 years.

At 2 degrees Celsius, extreme warming would occur in major population centers globally, including North America, the Mediterranean, and huge swathes of Asia.

"Limiting global warming to 1.5°C instead of 2°C could result in around 420 million fewer people being frequently exposed to extreme heatwaves, and about 65 million fewer people being exposed to exceptional heatwaves," the report said.

2. An ice-free Arctic

At 2 degrees C, it's far more likely that the Arctic Ocean — which is traditionally covered in thick sea ice during the summer — would be completely ice-free. This would trigger further warming, as bright ice reflects sunlight back into space, rather than letting it become absorbed in the oceans.

"There is high confidence that the probability of a sea-ice-free Arctic Ocean during summer is substantially higher at 2°C when compared to 1.5°C," write the authors.

At 2 degrees C — if we stop the warming there — there will likely be an ice-free Arctic once a decade. At 1.5 degrees C, such an event may occur just once a century.

3. Melting of massive ice sheets

At 2 degrees C, there would be about 10 more centimeters of sea level rise at century's end than at 1.5 degrees C, the authors write. But the trouble really brews beyond 2 degrees C. Such warming might trigger the collapse of Earth's major ice sheets, such as those that blanket Antarctica and Greenland. These would bring "multi-meter" rises in sea level, the report concludes.

Even at temperatures between 1.5 and 2 degrees C, the IPCC researchers found there's a "medium confidence" that such an ice sheet instability might be triggered.

Paleoclimate tells us that the difference between 1˚C and 2-3˚C of global warming can be the difference between a Greenland ice sheet and no Greenland ice sheet (Figure modified from @DrAndreaDutton et al.). Every fraction of a degree matters. #IPCC@IPCC_CHpic.twitter.com/8i7cGcuAxM

4. Coral Devastation

The planet's expansive and biodiverse coral reefs will have little time to adapt to dramatic changes in the oceans, specifically warming and acidification.

Over 90 percent of the heat trapped on Earth ultimately collects in the oceans — and repetitive marine heat waves have already proven dire to vast swathes of coral. What's more, increasing carbon dioxide in the air — which are at their highest levels in some 800,000 years — gradually gets absorbed by the oceans, increasing the water's acidity. This eats away at the coral's very skeletons.

If the temperature rises by 1.5 degrees C, corals will already have been hit hard, with a 70 percent global loss. A 2 degrees C jump means some 99 percent of corals will disappear from the planet, the report concludes.

BREAKING: #IPCC report reveals most coral reefs will be lost in next 30 years, even if we limit #globalwarming to 1.5°C (the goal of the Paris Agreement).

We must keep global warming BELOW 1.5°C for our Reef to have a future.

5. Rain, rain, rain

For every 1 degree Celsius (1.8 degrees Fahrenheit) of warming, the air can hold 7 percent more water. That means more rain, especially during big storms.

"Limiting global warming to 1.5°C limits risks of increases in heavy precipitation events in several regions," write the report's authors, citing places like Eastern North America, China, Japan, and Canada.

Hurricanes are also "projected to increase in intensity," as stronger storms are associated with heavier rainfall.

6. The poor get poorer

"Climate change is projected to be a poverty multiplier, which means that its impacts make the poor poorer and increase the total number of people living in poverty," the authors write.

Agricultural-dependent communities, including those that raise livestock, are expected to take a significant hit as temperatures rise.

"Global warming of 1.5°C (as opposed to 2ºC) is projected to reduce climate induced impacts on crop yield and nutritional content in some regions," the report reads. This includes areas in Asia, Africa, and South America.

What about where you live?

Not every area in the world, or your neighborhood, will be subjected to all these effects. But beyond a 1.5 degrees C jump, significant consequences are likely unavoidable in most every corner of the planet. California, for instance, will experience more alternating periods of severe drought and extreme deluges (this has already begun).

The IPCC wants to limit these effects, and doing so ultimately means ending our use of fossil fuels by 2050 — almost completely. Keeping temperature increases under 1.5 degrees C, however, is the first critical step.

"We're at a crossroads," the IPCC tweeted Sunday night. "What happens between now and 2030 is critical."

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